android - 适用于 Jelly Bean 但不适用于 Kitkat 的相机 API

Question

我有一个非常奇怪的问题。我的以下代码用于在单击按钮时拍照。它适用于 Jelly Bean 手机，但不适用于 Kitkat:

MainActivity.java:

package com.example.takepic;

import android.app.Activity;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.CameraInfo;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;


public class MainActivity extends Activity {
  private final static String DEBUG_TAG = "MakePhotoActivity";
  private Camera camera;
  private Button capture = null;
  private int cameraId = 0;

  @Override
  public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  capture = (Button)findViewById(R.id.captureBack);
  capture.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
         camera.startPreview(); //After this, nothing gets printed, and picture does not get taken
        System.out.println("Camera preview has started.");
            camera.takePicture(null, null, new PhotoHandler(getApplicationContext()));
    }
});
// do we have a camera?
if (!getPackageManager()
    .hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
  Toast.makeText(this, "No camera on this device", Toast.LENGTH_LONG)
      .show();
} else {
  cameraId = findBackFacingCamera();
  if (cameraId < 0) {
    Toast.makeText(this, "No back facing camera found.",
        Toast.LENGTH_LONG).show();
  } else {
    camera = Camera.open(cameraId);
  }
}
  }



 private int findBackFacingCamera() {
int cameraId = -1;
// Search for the front facing camera
int numberOfCameras = Camera.getNumberOfCameras();
for (int i = 0; i < numberOfCameras; i++) {
  CameraInfo info = new CameraInfo();
  Camera.getCameraInfo(i, info);
  if (info.facing == CameraInfo.CAMERA_FACING_BACK) {
    Log.d(DEBUG_TAG, "Camera found");
    cameraId = i;
    break;
  }
}
return cameraId;
}

  @Override
  protected void onPause() {
if (camera != null) {
  camera.release();
  camera = null;
}
super.onPause();
 }

} 

PhotoHandler.java:

package com.example.takepic;



import java.io.File;
import java.io.FileOutputStream;
import java.text.SimpleDateFormat;
import java.util.Date;

import android.content.Context;
import android.hardware.Camera;
import android.hardware.Camera.PictureCallback;
import android.os.Environment;
import android.util.Log;
import android.widget.Toast;

public class PhotoHandler implements PictureCallback {

  private final Context context;

  public PhotoHandler(Context context) {
    this.context = context;
  }

  @Override
 public void onPictureTaken(byte[] data, Camera camera) {

   File pictureFileDir = getDir();
  Toast.makeText(context, "Entered onPictureTaken", Toast.LENGTH_LONG).show();
   if (!pictureFileDir.exists() && !pictureFileDir.mkdirs()) {

  Log.d("Directory error", "Can't create directory to save image.");
  Toast.makeText(context, "Can't create directory to save image.",
      Toast.LENGTH_LONG).show();
  return;

 }

SimpleDateFormat dateFormat = new SimpleDateFormat("yyyymmddhhmmss");
String date = dateFormat.format(new Date());
String photoFile = "Picture_" + date + ".jpg";

String filename = pictureFileDir.getPath() + File.separator + photoFile;

File pictureFile = new File(filename);

try {
  FileOutputStream fos = new FileOutputStream(pictureFile);
  fos.write(data);
  fos.close();
  Toast.makeText(context, "New Image saved:" + photoFile,
      Toast.LENGTH_LONG).show();
} catch (Exception error) {
  Log.d("File saving error", "File" + filename + "not saved: "
      + error.getMessage());
  Toast.makeText(context, "Image could not be saved.",
      Toast.LENGTH_LONG).show();
  }
}

  private File getDir() {
  //  File sdDir =    Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
 File sdDir = new File(Environment.getExternalStorageDirectory().getAbsolutePath());
 Toast.makeText(context, ("Path : "+sdDir.getAbsolutePath()), Toast.LENGTH_LONG).show();
  return sdDir;
 }
} 

list 文件:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.takepic"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
    <activity
        android:name="com.example.takepic.MainActivity"
        android:label="@string/app_name" >
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>
</application>

为了调试目的，我已经放置了很多 toast 消息和打印语句。我没有在这里发布 logcat，因为当我在 KitKat 手机上运行它时，我在 logcat 上什么也得不到。没有异常或警告。

当我在 jellybean 手机上运行它时，它运行正常，显示所有 toasts 并打印并拍照。

当我在 Kitkat 上运行它时，在

之后我没有收到任何调试消息

camera.startPreview();
System.out.println("Camera preview has started.");

我怀疑问题出在 takePicture API 上，但我无法对其进行调试。

编辑

经过进一步分析，我找到了问题的原因。 PhotoHandler 对象被成功调用，但是 onPictureTaken 方法没有被调用，可能是因为它没有得到相机点击图片的信息。我不知道为什么。

Answer 1

我发现您没有为相机分配任何表面支架。为相机提供预览表面很重要。

根据这里的文档:

http://developer.android.com/guide/topics/media/camera.html

遵循文档建议的代码。在没有预览的情况下拍照是一个很大的安全问题。 Android 人员可能已经在 kitkat 中解决了这个问题。

您可能在粘贴此处时错过了那部分代码，因此请注意，还要检查您是否在 SurfaceHolder 的回调方法“onSurfaceCreated”中执行代码“camera.takePicture(null,null,callback)”。

您可以在上述链接中获取所有相关代码。